Dure Roche, Rocca Dura
[Tristram] won the tournament of the Castle of Maidens that standeth by the Hard Rock.
From this it appears that the Castle of the Hard Rock either was near to or identical with a Castle of Maidens. Roche Dure or Hard Rock may have been an earlier or an alternative name for it.
Perlesvaus | Early 13th century
Prose Tristan | 1230-1240